Telephone-exchange system.



D. M. TAGGART. TELEPHONE EXCHANGE SYSTEM APPLICATION FILED NOV. 17, 1917. I Patented Aug. 20,1918. i

//7 V/7/0//. 0a wson/W. Taqqarf in: mmRls psrznm, puomumrz. wasnmowu. o.

DAWSGN M. TAGGART, or need ORANGE, NEW JERSEY, AssIeNon ro wns'rnnn Erne- TRIC COMPANY, INCORPORATED, 015 -NEW YORK, Y., ,A CORPORATION OF NEW YORK.

To all whom it may concern:

' nection thereof with following Be it known that I, Dawson M. TAooAR'r,

a citizen of the United States, residing at East Orange,

in the county of 'Essex and State of New Jerse have invented certain newand useful Improvements-in Telephone-- Exchange Systems,-of which the following is a full, clear, concise, and exact description.

This invention relates to. telephone exchange systems, and more particularly to such systems of-the' central energy type employing Connecting or link circuits provided with apparatus for automatically applying ringing currentto the called-for line upon connection being made therewith. The object of this invention is to provide a system of this character in which the connecting or link circuit is provided with apparatus for preventing the application of ringing current to abusy line should the link circuit be connected therewith. V

In accordance with the various features of this invention, a connecting or link circ uit' with two local circuit relays is" provided which function and cooperate upon the con- The link circuit is also provided with apparatus by means of which, after the called-for station has responded and ringing current has been disconnected from: the line, it is imposs ble to agaln apply ringing on ent thereto upon the accidentaldisconnection of V the link or connecting circuit from the line and the reconnection therew th; I I1 For a more complete understandlng of this invention,reference'should be had to the, description cons dered in connection with the accompanying drawing illustrating one embodiment thereof.

In the drawing there is shown at'elephone line A extendingto a central 'ofiice X and wlth a cord circuit there suitably connected C. A telephoneline B-terminates at a central oflice Y, and a trunk-circuitD maybeemployed to, connect the cord circuit C with the telephone line B. The telephone lines A' and B and the cord circuit C are of the usual type, whilethe trunk circuit D embodies the above mentioned features of this invention.

The apparatus shown within the dotted lines Specificationjof Letters Patent.

the wanted a telephone line to con nect a source of ringing current therewith,-

- Patented Aug. 20,1918. Seria11\To.2 O2,5 16

in the upper 'left-handcorner of the drawing s located'at the central ofiice X, while the other apparatus shown in the drawing is located at the central oflice Y. This invention can probably be best understood from a 'desc'riptionbfthe operation of the system Illustrated in the drawing, and itwill be so described. *The operator at central oflice X, upon being advisedby the initiatingsubscriber A that'connection is desired with the line of subscriber B, may communicate over an order wire circuit (not shown) to .the oper ator at the central ollice Y, the number of line, whereupon the operator at central office Y assigns a trunk circuit to be used. Assuming that the assigned trunk-'cir; cuit is trunk circuit D, the'operatorat cen tral oflice X inserts plug 5"into jack 6 of the trunk circuit, thereby lighting the calling supervisory lamp '9. Trunk relay 7 also operates'over a circuit from battery through the winding of supervisory relay 8, ring contacts of the plug 5 and the jack 6, both windings of trunk'relay 7 and tip contacts of the jack '6 and the plug 5 to ground. 'Upon the operation of trunk relay 7, lamp 10 is lighted over a circuit from battery through lamp l0, resistance coil- 11, trunk relay 7 normal contact of tripping relay 12, normal contact of relay 13, and contact 14 of relay 1'5to ground. The operator at central otfice Y, observing the-lighted condition of the lamp 10, notes that the originating operator has connected the cord circuit C with the proper trunk'circuit. The operator-at central oflice. Y may thereupon test line B to determine-the idle or busy con alternate contact of 21, and the windingof cutofi" relay 23 to ground. .Relay22, in operating, causes the operation of relay 15 over a circuitfrom bat tery through .theu'pperwin'ding of relay '15,

and contacts'25 and 26 of relay '22 to ground. The operation of relay 15 opens the "circuit through the left-hand windingof-relay 22.

Relay 22 thereupon releases,

and establishes a circuit for relay 15, which may be traced from battery through "contact 27 and lower ping relay 12 is operated,

winding of relay 15, contact 28 of relay 22, sleeve contacts of the plug 20 and the jack 21, and the winding of cutoff relay 23 to ground. The operation of relay 15 removes a short circuit from the winding of ringing relay 30 which is of comparatively high resistance and which is now included in circuit with the lamp 10. The comparatively high resistance of this relay 30 causes the lamp 10 to be extinguished, while relay 30 operates, connecting to the line B a source of signal ing or ringing current '31 for operating call bell 32 at station B. p This signaling or ringing circuit may be traced from the source of current 31 through the winding of the tripping relay 12, contact 33 of relay 22, lower alternate contact of ringing relay 30, ring contacts of the plug 20 and the jack 21, the call bell 32 and the condenser at station B, tip contacts of the jack 21 and the plug 20, contact 3 of relay 15, upper alternate con; tact of ringing relay 30, and contact 35 of relay 22 to ground.

Upon the response of subscriber B,,tripthereby removing a short circuit from the right-hand winding of relay 13, which is thereupon included in circuit with the ringing relay 30 and operates. In operating, relay 13 establishes a locking circuit for itself from battery through the lamp 10, resistance coil 11, alternate contact of trunk relay 7, and right-- hand winding and alternate contact of relay 13 to ground. The closure of the alternate contact of relay 13 also establishes a short circuit for the ringing relay 30, which thereupon releases, disconnecting ringing current from the line. The resistance of the right-hand winding of relay 13 is comparatively high, so that the lamp 10 will not be lighted when lncluded in circuit therewith.

Upon the release of the ringing relay 30, supervisory relay 36 is operated, thereby short-circuiting the left-hand winding of trunk relay 7 The resistance in circuit with the winding of the supervisory relay 8 is thereby reduced, permitting the operation thereof. Upon the operation of supervisory relay 8 a shunt circuit including a resistance coil 37 is established about the calling supervisory lamp 9, whereby the lamp is extinguished.

If the plug 20 should accidentally be di connected from the ack 21 and reconnected therewith, relay 15 will first release upon the removal'of the plug, and upon the reinsertion thereof relay 22 will operate, followed by the operation and locking up of relay 15 and the release of relay 22 as hereinbefore described. Ringing current therefore will not be reconnected with the line Bv for the reason that relay 13 is locked up under control of the trunk relay 7.

At theconclusion of the conversation the subscrlbers restore the receivers to the switchhooks. The restoration of the receiver to the switchhook by subscriber B releases supervisory relay 36, thereby again including the left-hand winding of trunk relay 7 in circuit with the winding of supervisory relay 8. Relay 8 thereupon releases, causing the lighting of calling supervisory lamp 9, which, together with the answering supervisory lamp (not shown) of cord circuit C, serves as a disconnect signal to the operator at central oflice X. Plug 5 may thereupon be withdrawn from the jack (5. Trunk relay 7 then releases and the lamp 10 is lighted over a circuit from battery through lamp 10, resistance coil 11, normal contact of trunk relay 7 and contact 38 of relay 15 to ground. The lighting of this lamp 10 serves as a disconnect signal to the operator at central office Y, who may thereupon withdraw the plug 20 from jack 21, restoring all apparatus to normal condition.

Assuming that, after subscriber B has restored the receiver tothe switchhook and be before the connection is broken down, as fore described, the operator at central otlice X wishes to signal the subscriber B. The momentary removal of the plug 5 from a jack 6 followed by the reinsertion thereof causes ringing current to be connected with the line B. This is brought about in the following manner: When plug 5 is withdrawn from the jack 6, trunk relay 7 releases, thereupon opening the locking circuit of relay 13 which, in turn, releases. Upon the reinser: tion of the plug 5 into the jack 6, trunk relay 7 is again operated, whereupon an operating circuit is established through the winding of the ringing relay 30 which attracts its armatures, connecting ringing current to line B. The call bell at station'B is therefore operated and when subscriber B removes the receiver from the switchhook, ringing current is disconnected from the called line and the calling supervisory lamp 9 is lighted'in the manner hereinbefore described. If the op.- erator at central ofiice'X wishes to communicats with subscriber B, the actuation of a listening key 39 connects the operators telephone set in circuit so that this operator and the subscriber may converse.

If another trunk circuit similar to D era cord circuit .slm-llar to C is connected with another jack of line B when the'plug' 20 is inserted into the jack 21'thereof, relays 22' ing relay 30operates in the manner hereinbefore'described, but, since contacts 33 and 35 of the relay 22 current is not, and cannotbe, connected to the line B. Immediately upon the operation of theringing relay 3( relay 13 is connected across the tip and ring conductors of the trunk circuit D and is operated over a cir-. cuit from battery supplied through the other connected cord or trunk circuit, the ring contact of the plug thereof, ring contacts of the jacks of line B, ring contact of the plug 20, lower alternate contact of ringing relay 80, left-hand winding of relay 13, contact 40 of relay 22, upper alternate contactof relay 30, contact 34 of relay l5, tip contacts of the plug 20 and the ack 21, back to the other side of the battery in the other connected cord or trunk circuit through the tip contacts of the plug thereof and the jack engaged thereby. Relay 13, in operating, establishes a locking circuit through its righthand winding and also short-circuits the ringing relay 30, which disconnects the re lay 13 from the tip and ring conductors and closes through these conductors. Supervisory relay 36 then operates, ing the left-hand winding of lay 7, thereby permitting the operation of supervisory relay 8 to extinguish the calling supervisory lamp 9. Ringing current can not be connected to line B when the cord or trunk circuit previously connected there with is disconnected, for the reason that relay 13 is now locked up under control of the trunk relay 7. r p I This invention provides a simple system of the automatic ringing type in which it is a simple and easy matter to establish three-cornered connections.

What is claimed is:

1. A telephone exchange system comprising a telephone line, a link circuit for connecting therewith, a source of ringing current, a first relay in the link circuit respons'ive to the connection thereof with the line,

a second relay energized upon the response of the first relay, and a ringing relay responsive to the energization of the second relay to connect the source of ringing current to the line when the first relay is deenergized/ 2. A telephone exchange system compr1sing 'a telephone line, a link circuit for connecting therewith, a first relay in the link circuit energized upon the connection thereare now open, ringingshort-circuitthe trunk re-' relay. 7

ing a telephone'line,a link-circuit for con with the line, a second relay responsive to the energization of the first-relay to cause the deenergization of the first relay, a looking circuit forthe second relay completed upon the response thereof for-rendering it independent ofthe first relay, a ringing relay energized upon the response of the second relay, and a source of ringing current connected with the telephone line through normallyclose contacts of the first relay and normally open contacts of the ringing 4. A telephone exchange system comprising a telephone line, a link circuit for connecting therewith, a first relay in the link circuit energized upon connection with the telephone line, a second relay responsive to the energization of the first relay for causing the deenergizationthereof, a ringing relay, an operating circuit therefor completed upon the response of the second relay, and a source of ringing current connected to the line through contacts of the first relay when deenergized and contacts of the ringing relay when operated.

5. A telephone exchange system. comprising a telephone line, a link circuit connected therewith, a second link circuit, a first relay therein responsive to the connection thereof with the telephone line, a locking circuit for the first relay established upon the response thereof and including engaged contacts of both link circuits in the telephone line, a second relay energizedupon the response or the first relay to open the of with the line, a second relay responsive to r the energization of the first relay, .a mugresponse of the second relay, and a source of ringing current connected with the telephone line through contacts of the first relay when deenergized and contacts of the ringing relay when energized.

3. A telephone exchange system compris the .link circuits thereof with the initial energizing circuit thereof, a ringing relay operating upon the energization of the second relay, a] source of ringing, current, and a fourth relay cooperating with the ringing relay to control the connection of the source of ringing current to the telephone line and responsive to the operation of the thereo p r 6. A telephone exchange system comprising a telephone line, link circuits for connecting with the line, a first relay in one of energized upon connection telephone line, asecond relay responsive to relay, a ringing relay energized upon the response of the second relay, a source of ringing current, circuit leads connected with. the

the energization of the first telephone line, by the energization of the ringing relay and with the source of ringing current by the deenergizationv of the firstrelay when the line-connected with is idle, and a locking circuit'for the first relay 110 rlnging relay to cause the deenergization Copies of this patent may be obtained for nected with the same line, a ringing relay energized upon the response of the second relay, a source of ringing current, and circuit leads over Which current from said source is transmitted to the telephone line and including normally closed contacts of the first'relay and normally open contacts 01 the ringing relay.

In Witness whereof, I hereunto subscribe 1ny7na1ne this 14th day of November A. 1)., 191

DAWSON M. TAGGART.

five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

